In Europe Patent Laid Open No. 0 059 423 published on Sept. 8, 1982, there is disclosed an internal combustion engine cooling apparatus which generates steam within a water jacket, pressurizes the steam, cools the steam to liquefy the steam, decompresses the liquefied coolant to a normal pressure, and recirculates it to the water jacket.
In U.S. Pat. No. 3,448,729 granted to Persons on June 10, 1969, there is disclosed a boiling and cooling apparatus used to cool a V-type engine.
It is desirable for such a boiling and cooling apparatus to have a device which can furnish an adequate supply of coolant to the water jacket from a reservoir or low tank so as to maintain the coolant at a predetermined level within the water jacket. It has been proposed, in U.S. patent application Ser. No. 663,911, filed on Oct. 23, 1984, now U.S. Pat. No. 4,549,505, to provide a control device which controls a feed pump provided in a coolant supply passage connected between the reservoir and the water jacket. A level sensor, connected to the control device, is provided to monitor the level of the coolant contained in the water jacket. The control device drives the feed pump to maintain the coolant level above the predetermined value when the level sensor detects the coolant level falling below the predetermined value.
If such a boiling and cooling apparatus is applied to a V-type engine which normally has separate cylinder-head water jackets formed in the cylinder blocks of the respective banks, it is required to compensate for coolant level variations produced when the vehicle is rolling or running on a slope by providing a plurality of level sensors at different positions in the engine. This in turns increases the cost, sophisticates the coolant level control, and results in a slow coolant level control response.
In addition, bubbles form to unsettle the coolant surface in the cylinder-head water jackets of the respective banks so as to introduce errors in the coolant level measurement when the coolant is boiled.